A device that detects unevenness of a side surface of a tire is an example of a known technique for measuring unevenness of an object surface. Such a device includes a pair of optical sensors and a determination unit. To be specific, the optical sensors are disposed so as to oppose the outer side of a tire rotatably supported by a shaft, and measure respective distances to the outer surface. The determination unit receives detection signals from the optical sensors, and determines that the tire is unsatisfactory when the distance to the outer surface of the tire varies beyond the reference range.
A measurement device, such as a scanning tunneling microscope, is known which measures unevenness of a material surface by performing a two-dimensional operation. This measurement device generates an inclined waveform of an object surface along the Z axis with respect to the X or Y axis for each scan along the X or Y axis, and determines a peak to peak value of the waveform. In addition, the measurement device A/D-converts the values of the inclined waveform through the amplifier. Further, the gain of the amplifier is optimized on the basis of the p-p value for the latest scan.
An unevenness measurement device is known which scans an object surface to be measured with a probe, while keeping the probe separated from the object surface so as not to be brought into contact with the surface. This unevenness measurement device measures a capacitance between the object surface and the probe, which is a predetermined distance away from the object surface, while scanning the object surface with the probe, and then, determines a distance between the probe and the object surface on the basis of the determined capacitance.
As for power consumption, an electronic device is known which has a configuration in which a processor circuit operates a built-in sensor intermittently and shuts down power to the sensor during an idle state.
An object detection device is known which includes: a detection unit that is capable of detecting a target in a specific direction; an operation control unit that operates the detection unit over a predetermined period; a variable operation-frequency unit that causes the operation control unit to decrease the operational period of the detection unit when the detection unit detects the target; and an output generation unit that outputs an alarm signal when the detection unit consecutively detects the target during the detection operation of the decreased period.
A technique is known for decreasing the power consumption in a micro-electromechanical system (MEMS) by setting the sampling frequency in a power-saving mode to be lower than that in a normal mode.
In the related art, neither a device nor a method is known which detects an undulation of a measurement surface by causing a two-dimensional sensor to emit a sensing wave for distance measurement in a plurality of directions forming different lateral and vertical angles and to measure distances to objects, and which notifies a user of detection of the undulation. For example, such a device and method are utilized to detect an undulation of the ground, road or floor around a user, and to notify the user that an obstacle is present thereon.
In the case of notifying a user of detection of an undulation, it is desirable to notify the user of only undulations equal to or more than an allowable level depending on the purpose of the device or method. If the detection sensitivity is excessively higher or lower than the user expects, the user may feel unsatisfied. For example, in the above example of notifying the user of the detection of an obstacle, the user may feel inconvenienced when notified of the detection of a relatively low or small undulation, because such an undulation is less likely to be an obstacle.
Japanese Laid-open Patent Publication Nos. 03-179206, 04-104001, 09-33205, 2006-295956, 08-338879, and 2011-89980 are examples of related art, in particular, the above-described techniques and devices.